The Pothomorphe clade of Piper contains ten species of shrubs and vines that are native to the New World tropics. One of these, Piper umbellatum, has been introduced outside its native range, and has become successfully established in most wet tropical areas around the World. The species is rather weedy in its native range, and also in parts of the Old World, where it occurs along roadsides, in cultivated fields, and other disturbed habitats. In other parts of the Old World, however, it behaves much like a native plant and can only be found on forested slopes along mountain streams. This is the exact opposite of the expected pattern, and makes one question whether P. umbellatum is indeed New World in origin. Research analyzing the Pothomorphe clade was undertaken to help understand the origin and distribution of P. umbellatum in both the Old and New World. DNA was extracted from various Piper specimens and sequenced to examine nuclear ITS and chloroplast petA–psbJ sequences. The complete analysis revealed poor resolution among species, but indicates the New World origin of P. umbellatum. Additional data are clearly needed to further study and understand the relationships among populations of Pothomorphe around the world.